Propeller blade



Oct. 14, 1941. c. DoRNn-:R

PROPELLER BLADE Filed March 51, 193s lllalyem- I "alizee/l y lNVENTORCLA U05 oE/v/E/e.

. ATTORNEY Patented Oct. 14, 1941 PROPEILLEBI BLADE Claude Dornier,Friedrichshafen-on-the-Bodensee, Germany, assigner oi' one-half toDornier- `Werke G. m. b. H., Friedrichshafen-on-the- Bodensee, GermanyApplication March 31, 1938, Serial No. 199,165 In Germany April Z, 19374 Claims.

'I'he present invention relates to propellers, particularly for aircraftand more specifically to propeller blades which are made up of aplurality of parts which parts may be made of different materials.

The present invention is particularly useful in connection with variablepitch propellers the blades of which are made of wood.

It is an object of the present invention to provide a propeller bladewhich is' formed by two hollow shells which are held together by screwsor other suitable connecting means and the surface of which may beveneered. The blade according to the present `invention comprises ametal shaft from which a tongue extends into the blade for about onethird to two thirds of its length. Tongue and shaft may belongitudinally split into two parts which are held together by suitableconnecting means.

Further and other objects of the present invention will be hereinafterset forth in the accompanying specification and shown in the drawingwhich, by way of illustration, show what I now consider to be apreferned embodiment of my invention. v

In the drawing:

Figure 1 is a cross sectional view of a propeller blade according to thepresent invention.

Figure 2 is an isometric illustration of the core or tongue memberaccording to the present invention.

Figure 3 is a cross sectional view of a modified propeller bladeconstruction according to the present invention.

Figure 4 is an isometric illustration of the split tongue which is usedin connection with the construction shown in Figure 3.

Like parts are designated by like numerals in all figures of thedrawing.

Referring more particularly to Fig. 1 of the drawing, numerals I and 2designate the hollow shells which in conventional manner, form thepropeller blade proper and may be made of wood, Bakelite or a similarlight material. The shells are made of wood and are covered by means ofa veneer 4. The interiors of the shells I and 2 are provided withreinforcements 5 and 6 respectively through which bolts 3 extend whichhold the shells I and 2 together. The reinforcements may be in the formof longitudinal projections or in the form of a plurality of individuahboss-like projections. In the interior of the hollow blade a tonguelike' member I which is preferably made of metal is provided. l

The body which comprises the tongue mem- (Cl. T10-159) ber 1 isillustrated in Fig. 2. It consists of shaft 8 which is rotund, forged,pressed or cast and which is provided with a reset 25 for mounting theshaft 8 to the hub of the propeller. To the shaft 8 the tongue member 'Iis rigidly connected and is preferably made in one piece together withthe shaft or root 8. The root part 8 may by cylindrical and providedwith an annular groove 25 for rigid connection with the propeller huband providing for adjustment of the propeller pitch. Tongue 'I has across sectional configuration resembling the letter H; the cross sectionof the tongue diminishes towards the end, i. e. towards the point of thepropeller blade. Tongue I is provided with a plurality of bores 9 foraccommodating bolts 3. The tongue is therefore connected with a largepart of the shells forming the propeller blade the contour of which isindicated by means of the dotted line 22 and the centrifugal forces setup in the blade shells act on a comparatively large area and not on theroot of the blade body only as is the case with conventional propellerblades. Due to the peculiar configuration of the tongue or Ystem 1 thepropeller blade can have a very slender configuration from the root tothe point and the outer end of the blade can be made very slim as isdesired for aerodynamical reasons. If the cross section of tongue Iwould not diminish towards the outer end such favorable formation of thepropeller blade would not be possible. It must be noted that the tongueI does not extend into the extreme end of the blade at all.

In the modification o-f a blade construction according to the presentinvention and shown in Figs. 3 and 4 tongue and shaft are made of twoparts. of two hollow shells I0 and II which are held together by meansof a plurality of bolts I2 and which are covered by the veneer I3. 'I'hetongue which corresponds to tongue 'I in Figs. 1 and 2 is made of twohalves I4 and I5. These halves have substantially U-shaped crosssectional configuration and are bordered at their outer edges The tongueor stem halves are provided withA edge strips I6 and I1 respectivelywhich are provided with bores for accommodating bolts, screws, rivets orthe like for connecting the propeller shells I0 and II. Each of thetongue The propeller blade proper consists halves Il and I5 is madeof'one piece with the root or shaft parts I8 and I9 which together formthe rotund shaft. Each shaft half is provided with a bore or opening 20and 2| respectively through which a connecting bolt 28 may be extended.Bores 20 and 2| are widened out at their outer parts for accommodatingthe head and nut of the connecting bolt so that the rotund outerconfiguration is not interrupted by projecting parts of the bolt. Thetongue halves Il and l5 are supplementarily pressed together by thebolts I2 which extend through the bores 26 and 21.

The embodiment of the present invention shown in Figures 3 and 4 has theadvantage over the embodiment illustrated in Figs. l and 2 that thetongue is more rigidly connected with the blade shells. It is possibleto first individuallyH connect tongue half I4 with shell I0 and tonguehalf I5 with the shell II by means of screws, bolts, rivets or the like.'I'hereafter the two halves of the propeller blade can be connected bymeans of bolts I2 and the shaft or root halves I8 and I9 by means ofbolt 28 extending through the bores 2|) and 2|.

While I believe. the above described embodiments of my invention to bepreferred embodiments, I wish it to be understood that Ido not desire tobe limited to the exact details of design and construction shown anddescribed, for obvious -modiiications will occur to a person skilled inthe art.

I claim:

l. A propeller blade comprising a blade proper split by a cut extendingsubstantially along the trailing edge and the leading edge into twoparts, a stem member having a root portion and a tapered tongue portionof H-shaped cross sectional configuration and having a web portion andextending from said root portion and into the interior of said bladeproper and being so positioned that said web portion is substantiallyparallel to the blade surfaces, and connecting means extending throughsaid parts and through said web portion and rigidly connecting saidparts with said tongue portion and with one another,

"said root portion projecting from said blade proper and being soconstructed as to form the root of said blade. l

2. A longitudinally split propeller blade comprising a blade propersplit substantially longitudinally into two blade parts by a cutextending substantially along the edges `of the blade,

a stem member having a root portion anda tongue portion extending fromsaid root portion and into the interior of said blade proper, said rootportion projecting from said blade. proper and being so constructed asto form the root o! said blade, said stem member being longitudi-` nallysplit into two symmetric parts, said bladeV parts being individuallyrigidly connected with the tongue portions of said stem parts, andconnecting means extending through the tongue portions of said stemparts and through said blade parts and being accessible from the outsideof said blade parts and rigidly interconnecting said blade parts andsaid stern parts.

3. A longitudinally split propeller blade comprising a blade propersplit substantially longitudinally into two blade parts by a cutextending substantially along the edges of the blade, a stem memberhaving a root portion and a tongue portion extending from said rootportion and into the interior of said blade proper, said root portionprojecting from said blade proper and being so constructed as to formthe root of said blade, said stem member being longitudinally split intotwo symmetric parts, said blade parts being individually rigidlyconnected with the tongue portions of said stem parts, connecting meansextending through the tongue portions of said stem parts and throughsaid blade parts and being accessible from the outside of said bladeparts and rigidly interconnecting said blade parts and the tongueportions of said stem parts, and another connecting means extendingthrough and rigidly interconnecting the root portions of said stemparts.

4. A propeller blade having a surface forming hollow part substantiallylongitudinally split to form two half shell portions, a stem'memberhaving a tongue portion of H-shaped crosssectional configuration andincluding a web portion and a channel on either side thereof, saidtongue portion extending into said hollow part and between said halfshell portions with the web por-V tion positioned substantially paralleltothe blade surfaces, longitudinal bulges projectingninward from saidhalf shell portions and ilttingftightly into the channels of said tongueportion, fastening means extending through saidbulges and through saidweb portion and rigidly fastening said half shell portions to said stemmember and to one another. l

CLAUDE DORNIER.

